sters for 54 h, at which time all ticks were removed. Individual nymphs .... Anderson, J. F., R. C. Johnson, L. A. Magnarelli, F. W. Hyde, and J. E. Myers. 1986.
Vol. 24, No. 3
JOURNAL OF CLINICAL MICROBIOLOGY, Sept. 1986, p. 446-447
0095-1137/86/090446-02$02.00/0 Copyright X 1986, American Society for Microbiology
NOTES Concurrent Borrelia burgdorferi and Babesia microti Infection in Nymphal Ixodes damminit JOSEPH PIESMAN,t* THOMAS N. MATHER, SAM R. TELFORD III, AND ANDREW SPIELMAN Department of Tropical Public Health, Harvard School of Public Health, Boston, Massachusetts 02115 Received 28 February 1986/Accepted 22 May 1986
Ixodes dammini nymphs were examined for evidence of concurrent infection with Borrelia burgdorferi and Babesia microti. A total of 19 nymphs (18.6%) from Nantucket Island were simultaneously infected, as were 24 nymphs (8.2%) from Naushon Island. These observations are consistent with a common reservoir host for both I. dammini-transmitted pathogens.
reaction, modified for the detection of B. microti, has been described before (Piesman et al., in press). The remaining internal organs of each nymph (midgut, central ganglion, malpighian tubules, etc.) were dissected away from the cuticle in the original drop of saline. These tissues were mounted and squashed with a cover slip. The cover slip was then removed, and the slides were air dried, fixed in acetone, and stored at -20°C. Subsequently, these slides were treated with a 1:100 dilution of fluoresceinisothiocyanate-conjugated antibodies. The polyclonal antibody was produced in rabbits immunized with the Guilford strain of B. burgdorferi, kindly supplied by Alan Steere. Antibody-treated slides were processed and examined for spirochetes as previously described (11). We examined the association between babesial and spirochetal infections in nymphal I. dammini collected on Nantucket and Naushon Islands. Of the 102 nymphs collected on Nantucket Island, 19 (18.6%) were simultaneously infected with B. microti and B. burgdorferi (Table 1). Similarly, a total of 24 out of 293 nymphs (8.2%) from Naushon Island were dually infected. There was a significant association between babesial and spirochetal infections in nymphal I. dammini on Nantucket Island (chi-square = 5.65, P < 0.02) and Naushon Island (chi-square = 17.14, P < 0.001). The number of observed ticks with dual infection was greater than the chi-square expected value on both islands (dually infected ticks: Nantucket = 19 observed, chi-square expected = 13.5; Naushon = 24 observed, chi-square expected= 12.5). The positive association between babesial and spirochetal infections in nymphal I. dammini is consistent with a common reservoir host for both agents. Simultaneous infection with B. microti and B. burgdorferi has been described for Peromyscus leucopus and Microtus pennsylvanicus (2). Moreover, P. leucopus is thought to be the primary reservoir host for B. microti (10) and B. burgdorferi (1, 7). The dually infected nymphal I. dammini observed in our study probably acquired their infections by feeding as larvae on P. leucopus, the principal host for immature I. dammini (9). The spirochetes we observed in I. dammini ticks are presumably B. burgdorferi since this species is the only spirochete known to naturally infect I. dammini. However, the recently available genetic (3, 6) and monoclonal antibody probes (4), which are diagnostic for B. burgdorferi, should
Concurrent human infection by two Ixodes damminiborne pathogens, Borrelia burgdorferi and Babesia microti, has recently been described (5, 8, 12). Such dual infection could derive from the bites of two different ticks, each infected with one etiologic agent, or from the bite of a single tick simultaneously infected with both pathogens. Simultaneous Babesia and spirochetal infections occur in rodent reservoir hosts (2), thereby providing the opportunity for larval I. dammini to acquire both agents simultaneously and pass both pathogens transstadially to the vector nymphal stage. Accordingly, we collected questing nymphal I. dammini in sites endemic for human babesiosis and Lyme disease and determined whether these ticks were infected by B. microti and B. burgdorferi. Nymphal I. dammini ticks were collected from May through September 1985. Questing ticks were collected by dragging a corduroy or flannel flag through vegetation. Ticks were collected on the University of Massachusetts Field Station-Nantucket Island, as well as on Naushon Island, Mass. These study sites have been previously described (9). Nymphs collected from these study sites have been found to harbor B. microti, as well as B. burgdorferi (Piesman et al., Acta Trop., in press). All field-collected I. dammini were taken to the laboratory and held at 21°C and 95% relative humidity for
